Synthesis and alignment of liquid crystalline elastomers

Herbert, Katie M.; Fowler, Hayden E.; McCracken, Joselle M.; Schlafmann, Kyle R.; Koch, Jeremy A.; White, Timothy J.

doi:10.1038/s41578-021-00359-z

Cited by 321 publications

(284 citation statements)

References 141 publications

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“…T NI is higher than room temperature, demonstrating that the samples are in the nematic phase during stretching. The stress-strain curves of MQ 1 and LCMQs 2-4 illustrate that the stress plateau area becomes more obvious with the increasing of liquid crystal content, which is similar to 'soft elasticity' (Figure 4a) [43], which can be attributed to the induced alignment of the liquid crystal elements along the direction of the applied stress during the stretching process [32,44]. Moreover, the tensile strength of LCMQs 2-4 decreased from 4.15 MPa to 2.16 MPa, and the elongation at break decrease from 677% to 601% (Table 3).…”

Section: Mechanical Adaptability Of Mq 1 and The Lcmqsmentioning

confidence: 77%

Liquid Crystal-Based Organosilicone Elastomers with Supreme Mechanical Adaptability

et al. 2022

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Elastomers with supreme mechanical adaptability where the increasing stress under continuous deformation is significantly inhibited within a large deformation zone, are highly desired in many areas, such as artificial muscles, flexible and wearable electronics, and soft artificial-intelligence robots. Such system comprises the advantages of recoverable elasticity and internal compensation to external mechanical work. To obtain elastomer with supreme mechanical adaptability, a novel liquid crystal-based organosilicon elastomer (LCMQ) is developed in this work, which takes the advantages of reversible strain-induced phase transition of liquid crystal units in polymer matrix and the recoverable nano-sized fillers. The former is responsible for the inhibition of stress increasing during deformation, where the external work is mostly compensated by internal phase transition, and the latter provides tunable and sufficient high tensile strength. Such LCMQs were synthesized with 4-methoxyphenyl 4-(but-3-en-1-yloxy)benzoate (MBB) grafted thiol silicone oil (crosslinker-g-MBB) as crosslinking agent, vinyl terminated polydimethylsiloxane as base adhesive, and fumed silica as reinforcing filler by two-step thiol-ene “click” reaction. The obtained tensile strength and the elongation at break are better than previously reported values. Moreover, the resulting liquid crystal elastomers exhibit different mechanical behavior from conventional silicone rubbers. When the liquid crystal content increases from 1% (w/w) to 4% (w/w), the stress plateau for mechanical adaptability becomes clearer. Moreover, the liquid crystal elastomer has no obvious deformation from 25 °C to 120 °C and is expected to be used in industrial applications. It also provides a new template for the modification of organosilicon elastomers.

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Section: Mechanical Adaptability Of Mq 1 and The Lcmqsmentioning

confidence: 77%

Liquid Crystal-Based Organosilicone Elastomers with Supreme Mechanical Adaptability

et al. 2022

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“…The anisotropic step lengths in Eq. 2 turn the spheroid formed by the polymer chain in elastomers into an ellipsoid in the LCEs (Herbert et al, 2021), as shown in Figure 1B. The ratio between the two effective step lengths, r = l n /l p , representing the anisotropy for the nematic LCE, can be further expressed with the nematic order of the liquid crystal ordering, Q,…”

Section: Neo-classical Theory For Lcesmentioning

confidence: 99%

A Programmable Liquid Crystal Elastomer Metamaterials With Soft Elasticity

Liang

2022

Front. Robot. AI

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Liquid crystal elastomers (LCEs) are a rubbery network of polymers with ordered liquid crystal mesogens. The combination of rubber elasticity and the anisotropic liquid crystalline order gives exceptional mechanical properties, like soft elasticity, where near-constant stress accompanies large elastic deformation in the material. However, the soft elasticity in LCEs is often bounded by the intrinsic molecular interactions and structures, limiting the range of programmable mechanical properties and functionalities. Here, we demonstrate that the semi-soft elasticity of LCEs can be integrated into the framework of metamaterials to realize markedly programmabilities. Under uniaxial deformation, each state of the building blocks in metamaterials and the molecular composition of the nematic LCEs is associated with a distinctly different stress-strain relation that is fully elastic. Taking advantage of the tunable bending and stretching deformation enabled by the geometry of the building blocks and the semi-soft elasticity of the nematic LCE in the metamaterials, we can engineer the local stretch and stress at an unmet level of their counterpart composed by elastomers. Numerical simulations and analytical models are developed to relate the metamaterial geometries and the LCE soft elasticity to the mechanical responses. In addition, an elastic region with near-zero stiffness up to a stretch of 1.4 can be designed by connecting the compliant responses due to bending deformation and the soft elasticity in the LCE. We expect that the specialized mechanical tunability enabled by the LCE metamaterials can facilitate the development of advanced forms of mechanical metamaterials and impact the design of robotic systems.

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“…For widely used soft-connected systems, it is necessary not only to provide some mechanical strength under stress, but also to expand the stress platform as much as possible under harsh service conditions [ 9 , 10 ]. Liquid crystal elastomers [ 11 , 12 , 13 , 14 ], which can dissipate energy through reversible internal phase transition under external stimulation and have recoverable large deformation capacity [ 15 , 16 , 17 ], have become one of the best choices for mechanical adaptability materials [ 18 , 19 ]. Recently, White et al explored stress-induced phase transitions in elastomers with appreciable liquid crystal content and compared these responses to LCEs in the polydomain orientation [ 1 ].…”

Section: Introductionmentioning

confidence: 99%

The Effect of Phenyl Content on the Liquid Crystal-Based Organosilicone Elastomers with Mechanical Adaptability

2022

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An elastomer with mechanical adaptability is a new kind of polymer material in which the increasing stress under continuous deformation is significantly inhibited in a large deformation area. Liquid crystal-based organosilicone elastomers, which can dissipate energy through reversible internal phase transition under external stimulation and have recoverable large deformation capacity, have drawn much interest as mechanical adaptability materials. However, there is no good way to control the mechanical adaptability at present. For this purpose, we prepared a new liquid crystal-based phenyl silicone rubber (LCMVPQ) using two-step click reactions and systematically explored the effect of phenyl content on its mechanical adaptability to achieve the regulation of mechanical adaptability. With an increase in phenyl content in the LCMVPQs, phenyl can hinder the rearrangement of the mesogenic units along the applied stress direction, which enables the adjustment of mechanical adaptability to meet the needs of different situations. In addition, the introduction of the liquid crystal phase impedes the internal friction of the molecular chain movement of the LCMVPQs and reduces the damping performance of silicone rubber. This research achieves the regulation of elastomers with mechanical adaptability and is expected to be applied in practical application fields.

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Synthesis and alignment of liquid crystalline elastomers

Cited by 321 publications

References 141 publications

Liquid Crystal-Based Organosilicone Elastomers with Supreme Mechanical Adaptability

Liquid Crystal-Based Organosilicone Elastomers with Supreme Mechanical Adaptability

A Programmable Liquid Crystal Elastomer Metamaterials With Soft Elasticity

The Effect of Phenyl Content on the Liquid Crystal-Based Organosilicone Elastomers with Mechanical Adaptability

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